1. Field of the Invention
This invention relates to cellular polyurethane compositions and more particularly to a catalyst composition for use in promoting the formation of polyurethane foams.
2. Prior Art
The reaction of an isocyanato group with hydroxy groups can proceed at a significant rate because of the temperature of the reaction medium, but can be accelerated by the presence of an appropriate catalyst. Similarly, the reaction between the isocyanato group and water for the generation of a carbon dioxide blowing agent can be accelerated by a suitable catalyst. The dimerization and trimerization of isocyanates can also be accelerated by the proper catalyst.
The order of activity of numerous catalysts have been studied in simple systems, but such data has proven to be of little value in predicting the degree of suitability of a specific composition as a catalyst for the transformation of a precursor into a polyurethane foam under industrial conditions. Amine catalysts have been highly advantageous for promoting polyurethane polymerization; see Polyurethanes: Chemistry and Technology, Vol. I, Saunders and Frisch, Interscience Publishers, N.Y. (1962), at pages 138 - 139, 161 - 163 and 173 - 180. Quaternary ammonium compounds, which under the conditions of a prepolymerization reaction of a two-step process produce foamed polyurethane resins, decompose to liberate tertiary amines as disclosed in Reis, U.S. Pat. No. 2,779,689 and Parker, U.S. Pat. No. 2,981,700. Examples of quaternary ammonium compounds which are disclosed for this purpose are the essential neutral salts formed by the reaction of a tertiary amine such as N-methyl morpholine with the anhydride of a carboxylic acid such as acetic acid. Such quaternary salts have less catalytic activity than the tertiary amines from which they are derived.
Erner, U.S. Pat. No. 3,010,963, discloses the use as polyurethane foam catalysts of such quaternary hydroxyalkyl tertiary heterocyclic amine bases as N- .beta. -hydroxyalkyl-diazabicyclooctane hydroxide having the following formula: ##STR2## where: R is hydrogen or an alkyl group having 1 to 10 carbon atoms.
Patton et al, U.S. Pat. No. 3,766,103, disclose a method for preparing a co-catalyst for the manufacture of rigid plastics which co-catalyst comprises an adduct of 1,3,5-tris (N,N-dialkylaminoalkyl)-s-hexahydrotriazine, an alkylene oxide and water. The resulting hexahydrotriazine co-catalyst is completely outside the scope of the catalyst compositions of the present invention.
The preparation of a quaternary hydroxyalkyl tertiary amine base, e.g. dimethyl-bis [.beta. -oxy-ethyl]-ammonium hydroxide, also written as N,N-dimethyl-N,N-dihydroxyethyl ammonium hydroxide, is disclosed in Beilstein, Organische Chemie, Vol. IV (1922), at page 284. A process for producing such quaternary ammonium bases is disclosed in Ulrich, et al, U.S. Pat. No. 2,173,069, in which an alkylene oxide is reacted with a tertiary amine in aqueous medium having an initial pH of 8 to 9. Such products have been disclosed as being useful as additives in the printing of fabrics and in the preparation of artificial fibers, as well as in the preparation of dyestuff pastes and powders.
German Offenlegungschrift No. 1,801,822 discloses the preparation of such quaternary ammonium-hydroxyaryl compounds having the following formula: ##STR3## where: R.sub.1 is a higher molecular weight aliphatic group having, for example, 12 - 16 carbon atoms,
R.sub.2 is a monocyclic benzene group, PA1 R.sub.3 and R.sub.4 each is a low molecular weight aliphatic group, and PA1 A is at most a 2-membered ring containing aromatic groups.
The compounds are disclosed to have utility as bactericides and fungicides.
Laird et al, Journal Chemical Society, Part 3 (1969), at pages 1062 - 1068, disclose quaternary ammonium alkoxide compounds and Shechter et al, Industrial and Engineering Chemistry, Vol. 48 (1956), at pages 86 - 87, disclose quaternary ammonium hydroxide compounds. These latter references teach the reaction of an alkylene oxide, an alcohol and a tertiary amine. Neither of these compounds is disclosed to have utility as a polyurethane catalyst.